Siccative organic coating compositions have been applied to metal surfaces such as by spraying, dipping, rolling, centrifuged dip-spinning, etc. In recent years, various water-soluble resin-based paints and lacquers have been developed, and progress has been made toward the application of such coating systems by electrophoresis. The electrophoretic application of paint and lacquer involves the phenomena of electro-osmosis and electrolysis, as well as electrophoresis. In this method, an electric current is passed through the paint or lacquer solution while the article to be painted is made an electrode, usually the anode, in the paint or lacquer.
The electrodeposition of water-based coatings has been employed to process metal parts including small stamped parts such as nuts, bolts, and fasteners. The use of electrodeposition of siccative organic coatings on small parts has advantages over other methods of coating. For example, the process deposits a film of uniform thickness on essentially any conductive surface, even those which have sharp points and edges. The electrocoated film when applied, is relatively water-free and, thus, will not run or drip when taken out of the bath. The use of water-base coating compositions also is advantageous since they contain little or no organic solvents or other volatile organic compounds. Accordingly, such aqueous systems and processes do not require special precautions or equipment for handling any harmful volatile materials, and such aqueous systems and processes do not contribute to the problem of volatile organic emissions and air pollution.
It also is well known in the metal-finishing art that metal surfaces such as aluminum, ferrous and zinc surfaces may be provided with an inorganic phosphate coating by contacting the surfaces with an aqueous phosphating solution. The phosphate coating protects the metal surface to a limited extent against corrosion and serves primarily as an excellent base for the later application of a siccative organic coating composition such as paint, lacquer, varnish, primer, synthetic resin, enamel, and the like. Procedures also have been described in the art for improving the rust-resistance of metal articles by the application of a film of paint over phosphated surfaces. Although the application of a siccative coating over a phosphated metal surface improves the corrosion resistance properties of the metal, there continues to be a need to improve the corrosion resistance of electrophoretically painted metal surfaces. It is also desirable to develop coating formulations which impart improved and uniform torque (slip) properties to small coated articles such as coated fastener threads.
U.S. Pat. No. 4,952,293 describes a polymer electrodeposition process for preparing free-standing polymeric belts. The bath used to deposit the free-standing belts comprises a dispersion of electrically charged, thermoplastic film-forming polymer particles in an organic liquid dispersion medium substantially free of water. The polymer particles are substantially insoluble in the organic dispersion liquid medium at electrodeposition temperatures but are sufficiently soluble in the organic dispersion liquid medium at elevated drying temperatures to coalesce and form a viscous coating. Examples of the film-forming powders include polyvinylfluoride, and the dispersions may contain surfactants including fluoro surfactants including Zonyl FSC surfactants (cationic), charge control agents (other surfactants) and filler particles.
U.S. Pat. No. 4,544,677 describes foamable polycarbonate compositions comprising a mixture of a polycarbonate resin alone or with a polyester, a minor amount of a foaming agent, and a minor amount of an inorganic non-fibrous particulate nucleating agent alone, or with a particular organic polymeric material. The particular organic polymeric material may be a PTFE powder. Surfactants may also be included, and these are preferably nonionic surfactants such as silicones, polyglycol ethers, fluorocarbons, fatty acid derivatives, etc.
U.S. Pat. No. 4,252,878 describes a process for making hydrophobic polymeric separators wettable to electrolytic cell fluids by a post-manufacturing process of treating with fluorinated surface-active agents. The separators comprise various polymers including polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, polyfluoroethylene polyfluoropropylene, etc. Non-fluorine-containing polymers such as polyvinyl chloride also may be utilized. The surface-active agents employed are preferably fluorinated compounds which may be anionic, cationic, nonionic or amphoteric-type surfactants. A number of examples are given of each type of surfactant including non-ionic surfactants having perfluorinated hydrocarbon chains in their structure such as those available from DuPont under the trade designation Zonyl FSN.
U.S. Pat. No. 4,022,737 describes aqueous dispersions of hydrophobic polymer particles using surface-active polymers. Polyvinylidene particles may be stably dispersed in water by means of a surfactant which is a carboxy-functionalized copolymer. Other examples of hydrophobic polymer particles described in the patent include polyvinyl fluoride and polytetrafluoroethylene.